Electronic systems typically are produced from component parts that are independently designed and manufactured. For example, a typical personal computer includes a microprocessor, some type of memory device such as a dynamic random access memory and a number of other integrated circuits. These components are designed according to standards for various families of integrated circuits. Integrated circuits in a "family" are designed to recognize defined voltage levels as high and low logic values used by the circuits to communicate and process data. For example, the "transistor-transistor logic" or "TTL" family of integrated circuits typically recognize 0.7 to 0.8 volts as a low logic value and 2.0 to 2.4 volts as a high logic value. In the "complimentary metal-oxide semiconductor" or "CMOS" family, circuits use a voltage that is approximately equal to the power supply as a high logic level and ground potential as the low logic level. During normal operation of the electronic systems, the components communicate with each other to share data and control signals. To do so, the components often need to recognize logic levels for a different family of integrated circuits. Designers have developed various buffer circuits that convert logic levels from a circuit in one family to logic levels of a different family.
One type of buffer circuit converts TTL logic levels for use by a CMOS circuit. The buffer typically consists of two CMOS inverters coupled in series. Unfortunately, this design draws a significant standby current. In an integrated circuit, such as a dynamic random access memory, that has a number of inputs, the standby current could decrease the overall performance of the integrated circuit. With the input buffer in active-standby mode for long periods of time, this problem is exacerbated. Other buffers include schmitt triggers. The schmitt trigger similarly draws a significant standby current.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for buffer circuit that operates with an insignificant standby current.